Pulpstone



A ril 19 1949- H. W- BETH PULPSTONE Filed 1946' Patented Apr. 19, 1949PULPSTONE Hugo W. H. Beth, Worcester, Mass, assignor to Norton Company,Worcester,.Mass., a corporation of Massachusetts Application August 1,1946, Serial No. 687,583

The invention relates to segmental block type grinding wheels, and withregard to its more specific Efeatures to pulpstones.

:One object of the invention is to provide a stronger pulpstone. Anotherobject is to provide a pulpstone in which cracking at the ends caused byheat difierential is eliminated. Another object is to provide apulpstone with extra expansion joints at its ends to allow its abrasiveblocks more chance to expand and contract and thus eliminate crackingcaused by internal strains and heat differential. Another object is toprevent cracking due to heat differential at areas on the grindingsurface which are partly covered by logs and partly by water. Anotherobject is .to improve the pulpstone described in prior patent to ThureLarsson No. 2,141,608.

The invention accordingly consists in the tea tures of construction,combinations of elements and arrangements of parts as will beexemplified in the structure to be hereinafter described, and the scopeof the application of which will be indicated in the following claims.

In the accompanying drawing illustrating one of many possibleembodiments of the mechanical features of .this invention:

Figure 1 is a longitudinal sectional View of one half of .a pulpstoneconstructed in accordance with the invention and mounted upon a shaft.

Figure 2.is'a fragmentary end view of the pulpstone, partly broken awayto show the anchor bolts.

Figure "3 is a development of the cylindrical surface of the pulpstoneshowing the shape of .the segmental blocks and the relative size of thesmall and large blocks.

' The improved construction may be embodied in many difierent types ofpulpstone but is particularly applicable to that of the patenthereinb'efore mentioned. The present invention is herein shown asembodied in the type of pulpstone construction disclosed in said patent.

described in Patent No. 2,141,608, 1 provide a number of segmentalblocks Iii of bonded abrasive material having the projected shape shownin Figure '3 which is an irregular hexagon formed by two trapezoidswhose bases are coter- :minous. .I also provide a number of segmentaldilocks Ialla of bonded abrasive material having the proiectedshapeshown in .lifigure 3 which is an irregular pentagon formed by twotraperzoids whose bases are .coterminous. The blocks Illa are of theshape and size of the blocks it cut in halves, as will be more fullyexplained.

Z filaims. (Cl. 51-206.4.)

a washer =23.

Each block Ill and ma of bonded abrasive material is composed of anydesired type of abrasive such as-quartz, silicon carbide or fusedalumina, the latter being preferred, bonded together with suitable bondmaterial, preferably vitrified ceramic bond. Each block Ill and Illa istherefore formed of a mixture. of clay or frit with abrasive, suitablyplasticized as by the provision of a suitable amount of plastic clay andthe addition of water, then molded in a suitable mold and pressed underhigh pressure to cause the block to have sufiicient green strength forhandling. After each block Ill and Illa comes from the mold, it has anouter cylindrical surface Ii bounded by radial surfaces I2 and, as shownin Figures 1 and 3, fiat surfaces 93, and, as shown in Figure 2, a.plane inner surface I4. While the blocks ii) and Ilia are in a greenstate, I bore holes I5 therein, four holes It in block It and two holesI5 in block Ida; each hole I-5 having grooves IS in its side walls. Ithen form reentrant grooves I! in the inside corners where the radialfaces I2 join the-segmental face It. Each-groove II is adjacent to acorresponding groove I! in the adjacent block.

The blocks I0 and Ida are then iired in a kiln and the shape thusbecomes permanent and the material is thereby converted to vitrified-bonded abrasivematerial. I provide a quantity of bolts 2% having heads2i with grooves 22. I further provide an equal quantity of nuts 23,washers 24 and sleeves- 25. I place the sleeves 25 on the bolts 20abutting the heads 21. I then place the washers 2 5 against the ends ofthe sleeve-25, place the nuts 23 upon the outer threaded ends 23 of thebolts 2:0 and tighten the nuts 23. Thereby the bolts 20 are placed underinitial tension. I then place in each hole I5 a head 21 of a bolt 29 andfill the space with a suitable self setting cementfifi such as a mixtureof Portland cement and iron filings. This has em'ellerit holding power.Each block it thus has four bolt-sit projecting therefrom and *eachblock Ifia "has two 'boltsazt projecting therefrom, each bolt t'll beingencased by a sleeve 25 and having attached to it Each bolt 2i! is underinitial ten.- sion such that a considerable force is needed to move the'head '21 away from the washer 24 by even/a very slight distance. Eachbolt 23' is securely lockedxto its block I 0 and Ifla by reason of thefact that the cement 3t interlocks with the grooves 16 in the block andalso interlocks with the grooves 22 in the head 21'.

I provide a pair of center metal moldpieces (not shown), join them endto end and set them up upon an end mold piece of metal shaped to makethe ends of the pulpstone as shown in the drawings. I arrange the blocksIlla and it upon the end mold piece and concentrically about the centermold pieces in circular courses to form a cylindrical wall, with asuitable filler material 36 such as described in patent to Larsson No.2,054,171 between blocks. I lay the first or end course with blocks ma.I then lay courses with blocks until all but the top course which formsthe other end of the pulpstone have been laid. The top or opposite endcourse I again lay with blocks Illa. I locate a plurality of steelreinforcing hoops 3'! suitably wired together and forming in effect acage within the cylindrical space bonded by the blocks iii and Illa andthe outside of the central mold pieces. The cage formed of the hoops 37can be placed in position around the mold pieces, then the blocks builtup around them with pairs of bolts 28 between successive levels of hoops37. I use any temporary holding members such as clamps to hold theblocks i ll and l 0a closely together during construction of thepulpstone.

I form the blocks Ill with a hexagonal shape and blocks i 0a with apentagonal shape to fit together about the periphery of the pulpstone,as well illustrated in Figure 3, which breaks the joints in obtuseangles between the blocks around the surface of the stone in order toprovide continuous grinding at every iven point when work is heldagainst the stone. By forming these angular end joints between theabrasive blocks I provide continuous zigzag joints in the direction ofrotation of the wheel so that a continuous abrasive surface will bepresented to work touching all points along the length of the pulpstone.In this manner I avoid non-abrasive tracks which would be formed bycontinuous or interrupted plane circular joints about the surface of thewheel were I to use abrasive blocks with square ends, or any part ofwhose edges lay in planes normal to the axis of the pulpstone.

When I have completed the hollow cylindrical wall of blocks It and laand installed the reinforcing member 3?, as described, I place theentire assembly in a vulcanizing oven at a suitable temperature tovulcanize the filler material 36. Preferably I have erected the abrasivestructure and reinforcing members about the central mold pieces and uponthe end mold piece upon a carriage or car so that the whole structuremay be easily wheeled into the vulcanizing oven.

When the cylinder of abrasive blocks l0 and Illa has sufficiently cooledI pour concrete 40 in position between the central mold pieces and theblocks in and Illa and allow it to set. Before it hardens I shape theupper end of the stone the same as the shape of the lower end. I thenstrip the central and bottom mold pieces from the pulpstone.

The stone is now substantially complete except for features ofconstruction of the mounting which need not be described herein.

In the grinding of logs for pulp, the logs are pressed against the stoneat high pressure by hydraulic rams throughout the length of the stoneexcept for a short distance at each end of the stone amounting to aboutsix inches.

This tends to generate great heat in and throughout the segmental blockswhere the logs touch. To counteract this, water is played upon thesurface of the stone. However heat is still generated in the blockswhere the logs touch them. At either end of the pulpstone, the blocksare rendered much cooler by the water. This creates a sharp heatdifferential about the periphery of the pulpstone at both ends.

In pulpstones heretofore constructed substantially by the methoddescribed in which the blocks 19 were of full size throughout the lengthof the grinding surface, this heat differential tended to cause crackingof the full length end segmental blocks due to the great internalstrains. According to this invention I place small segmental blocks Illaat each end of the pulpstone so that there is a low heat differentialfrom end to end of the pulpstone. The small dimension of the end blocksresults in less dimensional change of the blocks and reduces internalstrain. An extra expansion joint around the pulpstone at each endresulting from the use of the small end blocks allows the blocks morechance to breathe or expand and contract due to heating and cooling.

The construction herein described has in addition all of the advantagesdescribed in Patent No. 2,141,608.

It will thus be seen that there has been provided by this invention anarticle in which the various objects hereinabove set forth together withmany thoroughly practical advantages are successfully achieved.

As many possible embodiments may be made of the above invention and asmany changes might be made in the embodiment above set forth, it is tobe understood that all matter hereinbefore set forth (or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. In a pulpstone, a plurality of blocks of bonded abrasive material,said blocks being arranged in courses to form a hollow cylinder ofrevolution, a hollow concrete core inside of said cylinder ofrevolution, means attaching said blocks to said hollow concrete core,each of the blocks in the courses of said blocks at the ends of saidpulpstone being appreciably shorter than each of the remaining blocksincluded between said courses measured in a direction parallel to theaxis of the said pulpstone.

2. In a pulpstone, a plurality of blocks of bonded abrasive material,said blocks being arranged to form a hollow cylinder of revolution, ahollow concrete core inside of said cylinder of revolution, meansattaching said blocks to said hollow concrete core, each of the blocksin the end courses of said blocks being of a length of each of the orderof one half the length of the blocks included between said end coursesmeasured in a direction parallel to the axis of said pulpstone.

HUGO W. H. BETH.

REFERENCES CITED The following references are of record in the LarssonDec. 27, 1938

